President Barack Obama is joining the cast of Entourage, sort of. The HBO show's star Adrian Grenier announced on his official Facebook page on Friday that he would make an Entourage movie if Obama agreed to make a cameo — and he's agreed, Grenier claims. "I promised to make the Entourage movie if he would do a cameo. He agreed," Grenier said, posted above a photo of himself with the President.